Macroborings in Otodus megalodon and Otodus chubutensis shark teeth from the submerged shelf of Onslow Bay,North Carolina,USA: implications for processes of lag deposit formation

Abstract

The shallow continental shelf in the Cape Fear Region of southwestern Onslow Bay, North Carolina, contains lag deposits with an abundance of megatoothed shark teeth belonging to Otodus megalodon (Agassiz 1835) and Otodus chubutensis (Ameghino 1906) that derive from the Pliocene Yorktown and Miocene Pungo River formations, respectively. These teeth exhibit different frequencies and orientations of macroborings identified as Gastrochaenolites torpedo Kelly and Bromley (1984 Kelly, S., and R. Bromley. 1984. “Ichnological Nomenclature of Clavate Borings.” Palaeontology 27: 793–807.Web of Science ®] , Google Scholar]), Gastrochaenolites lapidicus Kelly and Bromley (1984 Kelly, S., and R. Bromley. 1984. “Ichnological Nomenclature of Clavate Borings.” Palaeontology 27: 793–807.Web of Science ®] , Google Scholar]), Maeandropolydora sulcans Voigt (1965 Voigt, E. 1965. “Über parasitische Polychaeten in Kreide-Austern sowie einige andere in Muschelschalen bohrende Würmer.” Paläontologische Zeitschrift 39 (3–4): 193–211.Crossref] , Google Scholar]) and ?Entobia isp. attributed to endolithic bivalves, serpulid worms and clionaid sponges. Different frequencies and orientations of macroborings seen in lag deposits containing O. megalodon and O. chubutensis teeth are the result of repeated exhumation and reworking in response to bathymetrically controlled wave-based erosion during storm events and glacioeustatically driven sea-level cyclicity across Onslow Bay. Chronological ranges of O. megalodon and O. chubutensis teeth that contain macroborings indicate that these lag deposits may have been forming since the late early Miocene.